Embodiments herein generally relate to electrostatic printers and copiers or reproduction machines, and more particularly, concerns a system and method for aligning sheets within the media path and more particularly to embodiments that begin movement of a movable registration device before sheets have fully exited the movable registration device.
Certain sheet registration devices within media paths of printers and copiers require part of the registration device, in this case the carriage which performs the cross-process direction movement, to correct for sheet lateral error. The carriage also undergoes a reset move back to some home position after it registers a sheet. This movement back is normally done in the inter-document zone (IDZ) gap.
Depending on the pitch structure of the sheets/images on the photo-receptor, the sheet size, the incoming sheet registration errors, the input and output velocities and dimensional parameters, the accelerations and forces for the carriage reset move may become excessively large. Therefore, the registration device may not be able to complete the reset move within the time, velocity, and acceleration bounds provided. One approach is to always wait until sheets fully exit the carriage before beginning to return the carriage to the starting position.
The embodiments herein provide a system and a machine-implemented method that feeds at least one sheet through a media path in a process direction. The embodiments move the sheet registration carriage to its starting position before the sheet enters the sheet registration carriage. When the sheet is within the sheet registration carriage, the embodiments herein determine the amount of misalignment of the sheet using sensors positioned within the sheet registration carriage.
Further, when the sheet is within the sheet registration carriage, the embodiments herein align the sheet to a predetermined lateral position within the media path based on the amount of the misalignment. When performing the aligning process, the embodiments herein unevenly activate nips within the sheet registration carriage and simultaneously move the sheet registration carriage in a lateral direction perpendicular to the process direction.
In addition, when the sheet is still within the sheet registration carriage, the embodiments herein determine the lateral movement distance the sheet registration carriage will move when aligning the sheet. If the lateral movement distance of the sheet registration carriage exceeds a predetermined distance, the embodiments herein move the sheet registration carriage toward the starting position after the nips have released the sheet, but before the sheet has fully passed by the nips. To the contrary, if the lateral movement distance of the sheet registration carriage does not exceed the predetermined distance, the embodiments herein delay moving the sheet registration carriage toward the starting position until after the sheet has fully passed by the nips. The sheets are said to have fully passed by the nips when the trailing edge of the sheet is fully outside the nips.
This “predetermined distance” can comprise any appropriate distance depending upon the length of lateral travel that the sheet registration carriage is capable of moving, the speed at which the sheet registration carriage laterally moves, the speed at which the sheets are moving along the media path, etc. Thus, for example, the predetermined distance could be, one-third, one-quarter, one-fifth, one-eighth, etc. of the maximum lateral travel range of the sheet registration carriage. Further, the predetermined distance can be an absolute measure (5 mm, 7 mm, 11 mm, etc.) or can be a fraction, a percentage, etc. of the maximum lateral travel range of the sheet registration carriage.
An apparatus embodiment herein comprises a controller and a media path operatively connected to the controller. The media path feeds sheets in a process direction. A laterally movable sheet registration carriage is positioned within the media path and is operatively connected to the controller. The sheet registration carriage is movable in a lateral direction perpendicular to the process direction.
Sensors are positioned within the sheet registration carriage. The sensors are operatively connected to the sheet registration carriage. Further, rollers are within the sheet registration carriage. Opposing ones of the rollers form nips that move the sheets through the sheet registration carriage. The nips are points where two rollers meet and are positioned at a different locations within the sheet registration carriage.
The sensors determine the amount of misalignment of the sheets within the sheet registration carriage. The sheet registration carriage aligns the sheets to a predetermined lateral position within the media path based on the amount of the misalignment by simultaneously unevenly activating the nips within the sheet registration carriage and moving the sheet registration carriage in the lateral direction.
When the sheet is within the sheet registration carriage, the controller determines the lateral movement distance the sheet registration carriage will move during the aligning of the sheet. If the lateral movement distance exceeds a predetermined distance, the controller moves the sheet registration carriage toward a starting position after the nips have released the sheet, but before the sheet has fully passed by the nips. To the contrary, if the lateral movement distance does not exceed the predetermined distance, the controller delays moving the sheet registration carriage toward the starting position until after the sheet has fully passed by the nips.
These and other features are described in, or are apparent from, the following detailed description.